<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>
        span{ display: none; margin-left: 10px; color: #ff0000;}
    </style>
    <script src="../jquery-latest.js"></script>
    <script>
        $(function(){
            $('input').blur(function()
            {
                if( !$(this).val() ) {
                    $('span').css('display','inline-block');
                }
            });

            $('input').focus(function(){
                $('span').css('display','none');
            });
        });
    </script>
</head>
<body>

<input type="text" title=""/><span>필수항목입니다.</span><br/>
<input type="text" title=""/><span>필수항목입니다.</span><br/>
<input type="text" title=""/><span>필수항목입니다.</span><br/>
<input type="text" title=""/><span>필수항목입니다.</span><br/>

<br/>

<a href="http://stackoverflow.com/questions/1854556/check-if-inputs-are-empty-using-jquery">LINK</a>

</body>
</html>